Method for preparing comb polymer and use thereof for forming solid electrolyte

Abstract

The invention relates to a method for preparing a comb polymer comprising at least one step of grafting a telechelic polycarbonate / polyester having a free thiol group at one end, in the para position of a portion of the pentafluorophenyl groups of the monomeric units of a PPFS-type polymer, said grafting involving a nucleophilic substitution reaction between the thiol group of the telechelic polycarbonate / polyester and the fluorine atom in the para position of the pentafluorophenyl group. It further relates to the use of such a comb polymer to form a solid electrolyte.

Description

Technical field

[0001] The present invention relates to a novel method for preparing a comb polymer, and to the comb polymer thus obtained.

[0002] Such comb polymers can be used, in combination with alkali or alkaline earth metal salts, to form solid electrolytes, which find particularly advantageous applications in different electrochemical systems or devices, in particular in rechargeable batteries, for example lithium batteries. Prior art

[0003] Classically, the operating principle of an electrochemical generator is based on the insertion and removal, also called "deinsertion", of an alkali metal ion or a proton, into and from the positive electrode, and the deposition or extraction of this ion, onto and from the negative electrode.

[0004] The main systems use the lithium cation as the transport ionic species. In the case of a lithium accumulator, for example, the lithium cation extracted from the positive electrode during battery charging is deposited on the negative electrode, and conversely, it is extracted from the negative electrode to be intercalated in the positive electrode during discharge.

[0005] The transport of the proton or the alkali or alkaline-earth cation, in particular the lithium cation, between the positive electrode and the negative electrode, is ensured by an ionic conductive electrolyte.

[0006] The formulation of the electrolyte used is essential for the performance of the electrochemical system, particularly when it is used at very low or very high temperatures. The ionic conductivity of the electrolyte determines the efficiency of the electrochemical system, given that it affects the mobility of ions between the positive and negative electrodes. Other parameters also play a role in the choice of the electrolyte used. These include its thermal, chemical or electrochemical stability within the electrochemical system, as well as economic, safety and environmental criteria, including the toxicity of the electrolyte.

[0007] Conventional electrolytes are typically produced by dissolving a metal cation salt in an organic or aqueous medium, and require a separator to provide insulation between the anode and the cathode for the development of a complete electrochemical system.

[0008] As such, solid-state electrolytes (SSEs) represent one of the most promising alternatives to conventional electrolytes. Lithium batteries, using solid-state electrolytes, are considered the next generation of energy storage devices, allowing higher energy densities and increased safety due to the absence of solvents. SSEs can be classified into three categories: inorganic solid electrolytes (ISEs), polymeric solid electrolytes (SPEs) and hybrid solid electrolytes (HSEs).Particular attention is paid to SPEs and HSEs, solid polymer-based electrolytes, due to the high flexibility of these electrolytes, which allows their use in the development of batteries with reduced thickness and greater flexibility.

[0009] Similar to a liquid electrolyte, these polymer-based solid electrolytes are composed of a host polymer in which an alkali or alkaline earth metal salt is dissolved. Historically, the most widespread SPEs and HSEs, particularly for lithium electrochemical devices, have been based on polyethers, and more specifically on poly(ethylene glycol), also called poly(oxyethylene) (POE) [1]. However, the use of this type of polymer has several limitations. In particular, POE is largely crystalline (the crystallinity of pure POE is around 75-80% at room temperature), which leads to a loss of ionic conductivity of the POE-based solid electrolyte below its melting temperature (around 60-65°C). The mechanical stability of POE is also insufficient at high temperatures (above 60°C) where it conducts ions well. Moreover, POE has a narrow electrochemical stability window (< 3.9 V vs.Li / Li +< ), which makes this type of SPEs suitable only for their implementation with low potential cathodes, such as LiFePO 4 (LFP) type.

[0010] In fact, alternative polymers have been developed in recent years, including polycarbonates and more specifically poly(trimethylene carbonate) (PTMC). PTMC provides improved performance compared to POE in terms of electrochemical stability (up to 5.0 V vs. Li / Li +< ), higher ion transport number (t + ≈0.8) and thermal stability. However, these polymers have limited mechanical performance.

[0011] In order to overcome these limitations, it has been proposed to synthesize copolymers [2-4], comprising a rigid block, providing mechanical properties suitable for their use as an electrolyte, and an ionically conductive block. These copolymers can be of the block copolymer type formed from different polymers or of the graft copolymer type, also called comb polymers, composed of a main polymer chain, onto which pendant polymer chains are grafted.

[0012] Recently, the synthesis of comb polymers comprising a poly(2,3,4,5,6-pentafluorostyrene) (PPFS) main chain carrying poly(ethylene oxide) or poly(trimethylene carbonate) side chains, grafted in para pentafluorophenyl groups of the main chain via ether linkages [5-6].

[0013] Another example of a comb polymer comprising a main chain formed from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers bearing side chains is described in Ott et al., Chem. Comm., 30: 3516-3518 (2008). Polymers formed from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers are also described in Cai et al., Polymer Chemistry, 3: 1061-1068 (2012), and Cho et al., Polymers, 12: 1-14 (2020).

[0014] These comb polymers can in particular be formed by grafting the polymers intended to form the side polymer chains of the comb polymer directly onto the PPFS-type polymer. The grafting involves bringing the PPFS-type polymer into contact with a strong base, in particular sodium hydride (NaH), sodium hydroxide (NaOH) or potassium hydroxide (KOH), to carry out the so-called "para click" substitution reaction between the fluorine atom in position para pentafluorophenyl groups of the monomeric units of the PPFS type chain, and a hydroxyl function carried by the polymer to be grafted, for example a PTMC.

[0015] However, the inventors have found that the use of these strong bases to form the side chains of the comb polymer was likely to cause secondary trans-carbonation or trans-esterification reactions, leading to a reorganization of the PTMC type chains, with the consequence of the annihilation of the control of the ends of the chains of the polymer to be grafted, for example PTMC (elimination of the terminal hydroxyl function carried by the polymer to be grafted), and the increase in the polydispersity of the chains.

[0016] An analysis by size exclusion chromatography (SEC) makes it possible to highlight the impact of the presence of a strong base on the behavior of PTMC at the desired reaction temperature for grafting (65°C) ( Figure 17 ).

[0017] These side reactions in the presence of a strong base thus affect the reproducibility of the comb polymer synthesis, a loss of control of the grafting rate and the polydispersity of the grafted side chains, and have the consequence of making it difficult to optimize the comb polymers formed in order to increase the performance of the solid electrolytes prepared from these polymers.

[0018] There remains a need to propose a new route for the synthesis of comb-shaped ionic conductive polymers, making it possible to improve the control of the characteristics of the polymers obtained, in particular in terms of grafting rate, chain length and polydispersity of the pendant chains, and thus to optimize the performance of the solid electrolytes formed from these polymers.

[0019] The present invention aims precisely to meet this need. Summary of the invention

[0020] The invention thus relates, according to a first of its aspects, to a process for preparing a comb polymer comprising at least the steps consisting of: (i) having a polymer formed from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, called a “PPFS-type polymer”, intended to form the main chain of the comb polymer; (ii) having at least one polymer, called a “telechelic polycarbonate / polyester”, intended to form side chains of said comb polymer, said polymer being formed from at least one cyclic monomer with five to eight members chosen from lactones and cyclic carbonates, and having at least one hydroxyl function at one of its ends, and a free thiol function, in particular at the other of its ends; and (iii) grafting said telechelic polycarbonate / polyester, in position paraof a part of the pentafluorophenyl groups of the monomeric units of the PPFS type polymer, said grafting involving a nucleophilic substitution reaction between the thiol function carried by the telechelic polycarbonate / polyester and the fluorine atom in position para of the pentafluorophenyl group.

[0021] A "comb polymer," also known as a branched or branched copolymer, means a polymer that has a linear polymeric main chain and at least two side chains or pendant chains attached to the main chain at points between the two ends of the main chain, called branch points or branch points. Unlike linear polymers that have non-polymeric side groups or pendant groups, the side chains of comb polymers are oligomers, polymers, or copolymers.

[0022] In particular, a comb polymer is distinct from so-called hyperbranched or hyper-ramified polymer networks. In particular, the side polymer chains carried by the main chain of the comb polymer according to the invention do not themselves carry side polymer chains.

[0023] In the remainder of the text, the comb polymer obtained according to the invention will be referred to more simply as “comb polymer” or “comb polymer”.

[0024] In the present description, in the absence of contrary indications, the term "polymer" will be used to designate, in the broad sense, both homopolymers and copolymers. By "copolymer" is meant a polymer derived from at least two different species of monomers.

[0025] In the context of the present invention, the term "monomer unit" means the smallest constituent unit whose repetition leads to a polymer chain.

[0026] At the end of the grafting step (iii) of the process of the invention, the PPFS type polymer thus has polycarbonate / polyester chains derived from said telechelic polycarbonate / polyester polymer(s), linked in position para of a part of the pentafluorophenyl groups via thioether bonds.

[0027] The invention thus relates, according to another of its aspects, to a comb polymer, in particular as obtained according to the process of the invention described above, comprising a main chain of PPFS type formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers, a portion of the monomeric units of the main chain carrying polymeric side chains, called polycarbonate / polyester chains, formed from at least one cyclic monomer of five to eight members chosen from lactones and cyclic carbonates; said polymeric side chains being grafted in para pentafluorophenyl groups via thioether bonds.

[0028] Advantageously, as detailed in the remainder of the text, the nucleophilic substitution reaction for the grafting of said telechelic polycarbonates / polyesters can be carried out in the presence of an aprotic base weaker than sodium hydride, sodium hydroxide and potassium hydroxide, preferably an aprotic base having a pKa strictly less than 15 and strictly greater than 10. In particular, the nucleophilic substitution reaction can be carried out in the presence of a base having a pKa strictly less than 14, more particularly less than or equal to 13 and strictly greater than 10, or even between 10.2 and 13, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), triethylamine (TEA) or potassium carbonate (K 2 CO 3 ), in particular DBU or TEA.

[0029] Thus, the preparation of the comb polymers according to the invention makes it possible to avoid the secondary reactions of trans-esterification or trans-carbonation of polycarbonate / polyester type polymers observed in the presence of a strong base.

[0030] Advantageously, the method of the invention thus allows excellent control of the grafting rate of polycarbonate / polyester type side chains.

[0031] Also, the method of the invention allows a great variability of the grafting rate in side chains of the comb polymer obtained. The grafting rate can be more particularly adjusted by varying the molar ratio between said polycarbonate / telechelic polyester polymers and said PPFS type polymer.

[0032] Advantageously, the molar grafting rate of the polycarbonate / polyester side chains can thus be greater than or equal to 1% and up to approximately 100%, in particular be between 5% and 90%, more particularly between 5% and 75%, or even between 10% and 60%. In a particular embodiment, the grafting rate can be strictly greater than 35%, in particular be between 38% and 75% and more particularly between 40% and 60%.

[0033] Furthermore, it is to the inventors' credit to have developed a synthesis method enabling access to polycarbonate / telechelic polyester polymers of controlled structure, implemented according to the process of the invention to form the side chains of the comb polymer.

[0034] As detailed in the remainder of the text, the telechelic polycarbonate / polyester polymers can be obtained in a single step by ring-opening polymerization of one or more cyclic monomers as described above, for example trimethylene carbonate and / or ε-caprolactone, in the presence of at least one initiator which is a mono or polyalcohol, in particular a monoalcohol, carrying a free thiol function, in particular a mercaptoalkanol, for example 6-mercaptohexan-1-ol, and a catalyst, preferably an organic catalyst and more preferably chosen from diphenyl phosphate (DPP) and 1,1' binaphthyl 2,2' diyl hydrogen phosphate (BNPH).

[0035] Advantageously, this method of synthesizing telechelic polycarbonates / polyesters used according to the invention allows excellent control of the polymerization, in particular of the molar mass and the polydispersity of the telechelic polycarbonates / polyesters obtained.

[0036] Advantageously, the telechelic polycarbonates / polyesters obtained have a low polydispersity index, advantageously strictly less than 1.2, preferably between 1 and 1.1.

[0037] Also, this synthesis method allows access to excellent chemoselectivity of the polymerization, in that at the end of this synthesis, at least 70% of the polycarbonate / polyester chains formed have the desired thiol function at their end.

[0038] Furthermore, advantageously, as detailed in the remainder of the text, the inventors have developed a method for purifying the comb polymer obtained according to the invention, which is easy to implement and makes it possible to eliminate the polycarbonate / polyester chains which have not been grafted onto the PPFS type polymer.

[0039] The method for synthesizing telechelic polycarbonates / polyesters intended to form the side chains of the comb polymer according to the invention, combined with the aforementioned advantages linked to the use of a weaker base for the grafting of these telechelic polycarbonates / polyesters via thioether functions and to a purification of the product obtained, makes it possible to access, in a reproducible manner, comb polymers of good purity and controlled structure, in particular having grafted chains of controlled molar mass and low polydispersity.

[0040] It is thus possible to vary the characteristics of the comb polymer, for example in terms of grafting rate and length of the side chains, so as to optimize the performance of the solid electrolyte formed from these polymers.

[0041] Advantageously, the hydroxyl functions at the ends of the grafted polycarbonate / polyester chains of the comb polymer according to the invention are protected. As detailed in the rest of the text, the protection of the hydroxyl functions can be more particularly carried out at the level of the comb polymer obtained at the end of step (iii), before or after purification, by reaction of said hydroxyl function(s) at the ends of the side polycarbonate / polyester chains, with at least one compound, called a protective agent, chosen from acyl chlorides, acid anhydrides and isocyanates.

[0042] The comb polymers according to the invention find particularly advantageous applications for forming, in combination with at least one alkali or alkaline-earth metal salt, a solid electrolyte.

[0043] By "solid electrolyte" is meant an electrolyte excluding the presence of a component in liquid form, and acting both as a separator and as an ionic conductor in an electrochemical system. The solid electrolyte according to the invention is more particularly in the form of a solid electrolytic film or membrane in an electrochemical system.

[0044] As detailed in the remainder of the text, the solid electrolytes prepared according to the invention may be of the solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type. The solid electrolyte films or membranes prepared according to the invention advantageously exhibit good flexibility.

[0045] The invention thus relates, according to another of its aspects, to the use of at least one comb polymer according to the invention, in particular as obtained according to the process of the invention, to form, in combination with at least one alkali or alkaline-earth metal salt, a solid electrolyte intended for an electrochemical system, in particular for a rechargeable battery, in particular a lithium battery.

[0046] The invention also relates to a solid electrolyte, in particular of the solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type, comprising, or even being formed from: at least one comb polymer according to the invention, in particular obtained according to the process of the invention, preferably the hydroxyl functions of which at the ends of the grafted side chains are protected; at least one alkali or alkaline-earth metal salt, in particular a lithium salt; and optionally one or more inorganic fillers, in particular chosen from the conductive fillers and the non-conductive fillers of the alkali or alkaline-earth cation(s), in particular lithium.

[0047] The solid electrolytes formed according to the invention can find applications in various electrochemical systems, in particular in energy storage systems, in particular in rechargeable batteries, in particular lithium batteries.

[0048] Thus, the invention also relates to the use of a solid electrolyte according to the invention in an electrochemical system, in particular in a lithium battery.

[0049] It also relates to an electrochemical system, in particular an energy storage device, in particular a rechargeable battery, in particular a lithium battery, in particular a lithium-ion or lithium-metal battery, comprising a solid electrolyte, in particular a solid electrolyte film as defined previously.

[0050] As illustrated in the examples which follow, the solid electrolytes obtained from the comb polymers according to the invention lead to lithium batteries having excellent performances, in particular a high ionic conductivity, for example greater than or equal to 10 -7< S.cm -1< at 60°C, in particular greater than or equal to 10 -6< S.cm -1< , advantageously greater than or equal to 10 -5< S.cm -1< .

[0051] The solid electrolytes prepared from the comb polymers according to the invention also exhibit good mechanical strength and high thermal stability (which ensures the safety of the energy storage devices comprising them).

[0052] An electrochemical system, for example a lithium battery, comprising a solid electrolyte according to the invention, can operate over a wide temperature range, preferably between 20°C and 100°C, more preferably between 40°C and 80°C.

[0053] Advantageously, a solid electrolyte based on a comb polymer according to the invention, in particular comprising PTMC type side chains, can be advantageously implemented in high energy density batteries, in combination with so-called "high" potential positive electrodes, i.e. operating at a potential difference greater than 4 V versus Li / Li +< , such as Li 0< vs. LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 (NMC) batteries without impacting the thermal and electrochemical stability of the electrolyte.

[0054] Other characteristics, variants and advantages of the process for preparing a comb polymer according to the invention, of the comb polymer obtained and of its implementation in an electrochemical system, will emerge more clearly on reading the description, examples and figures which follow, given for illustrative and non-limiting purposes of the invention.

[0055] In the context of the invention, the following terms are understood to mean: “C 1-z” where t and z are integers, a carbon chain which may have from t to z carbon atoms; for example C 1-4 a carbon chain which may have from 1 to 4 carbon atoms; “alkyl”, a saturated aliphatic group, linear or branched; for example a C 1-4 -alkyl group represents a carbon chain of 1 to 4 carbon atoms, linear or branched, more particularly a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl; "alkylene", a saturated, linear or branched, divalent radical derived from an alkyl. For example, a C 1 -C 3 -alkylene group represents a saturated, linear or branched carbon chain of 1 to 3 carbon atoms, for example methylene, ethylene, 1-methylethylene or propylene. "polycyclic group", a group having two or more nuclei (cycles), fused (ortho-fused or ortho- and peri-fused) to each other, i.e. having, two by two, at least two carbons in common. "heterocycle", a cyclic group, preferably 4-, 5- or 6-membered, comprising one or more heteroatoms, in particular chosen from oxygen, sulfur and nitrogen. The mono- or poly(hetero)cyclic groups according to the invention may be unsaturated, partially saturated or saturated. An aromatic cycle can be benzene in particular.

[0056] In the rest of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the limits are included, unless otherwise stated. Brief description of the drawings

[0057] [ Fig 1 ] represents the intensity of the measurement signal obtained by nuclear magnetic resonance (NMR) of 19< F as a function of the chemical shift, expressed in ppm, for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-03") synthesized in Example 1.1. [ Fig 2] represents the elution diagram obtained by Size Exclusion Chromatography (SEC) in THF at 30°C (TDS calibration), as a function of the retention volume, obtained for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-03") synthesized in Example 1.1. The ordinate represents the detection obtained by an intrinsic viscosity detector (IV-DP), low angle light scattering (LALS), right angle light scattering (RALS), and a refractomer (RI). [ Fig 3 ] represents the elution diagram obtained by CES (THF, 30°C, TDS calibration), as a function of the retention volume, obtained for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-Em-01") synthesized in example 1.2. [ Fig 4] represents the intensity of the measurement signal obtained by nuclear magnetic resonance (NMR) of 19< F as a function of the chemical shift, expressed in ppm, for the polymer poly(2,3,4,5,6-pentafluorostyrene) ("PPFS-Em-01") synthesized in example 1.2. [ Fig 5 ] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the telechelic poly(trimethylene carbonate) ("SH-PTMC-OH-01") synthesized in example 2.1. [ Fig 6 ] represents the elution diagram obtained by CES (THF, 30°C, universal calibration), as a function of the retention volume, obtained for the telechelic poly(trimethylene carbonate) ("SH-PTMC-OH-01") synthesized in example 2.1. The ordinate represents the detection obtained by a refractometer (RI). [ Fig 7] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the telechelic poly(trimethylene carbonate) ("SH-PTMC-OH-02") synthesized in example 2.2. [ Fig 8 ] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-01") synthesized in example 3.1. [ Fig 9 ] represents the intensity of the measurement signal obtained by 19< F NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-01") synthesized in example 3.1. [ Fig 10] represents the elution diagram obtained by CES (THF, 30°C, TDS calibration), as a function of the retention volume, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-01") synthesized in example 3.1. [ Fig 11 ] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-02") synthesized in example 3.2. [ Fig 12 ] represents the elution diagram obtained by CES (THF, 30°C, TDS calibration), as a function of the retention volume, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(trimethylene carbonate) grafts ("PPFS-gS-PTMC-OH-02") synthesized in example 3.2. [ Fig 13] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the comb copolymer poly(2,3,4,5,6-pentafluorostyrene) bearing poly(trimethylene carbonate) grafts after protection of the ends of the side chains ("PPFS-gS-PTMC-Et-01") according to example 3.3. [ Fig 14 ] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the telechelic poly(ε-caprolactone) ("SH-PCL-OH-01") synthesized in example 4.1. [ Fig 15 ] represents the intensity of the measurement signal obtained by 1< H NMR as a function of the chemical shift, expressed in ppm, for the poly(2,3,4,5,6-pentafluorostyrene) comb copolymer carrying poly(ε-caprolactone) grafts ("PPFS-gS-PCL-OH-01") synthesized in example 4.2. [ Fig 16] represents the elution diagram obtained by CES (THF, 30°C, TDS calibration), as a function of the retention volume, for the telechelic poly(ε-caprolactone) ("SH-PCL-OH-01") synthesized in example 4.1, and for the comb copolymer poly(2,3,4,5,6-pentafluorostyrene) bearing poly(ε-caprolactone) grafts ("PPFS-gS-PCL-OH-01") synthesized in example 4.2. The ordinate represents the detection obtained by an intrinsic viscosity detector (IV-DP). [ Fig 17 ] represents the elution diagram obtained CES (THF, 30°C, universal calibration), as a function of the retention volume, for a PTMC before (“PTMC”) and after contact with NaH at 65°C (“PTMC+NaH”). [ Fig 18] represents the evolution of the ionic conductivity (in S.cm -1< ) ​​as a function of the temperature (T in °C, and 1000 / T, T being expressed in degrees Kelvin) for the solid electrolytes based on the comb polymers "PPFS-g 0.5 -S-PTMC 3700 -Et", "PPFS-g 0.4 -S-PTMC 5500 -Et", "PPFS-g 0.2 -S-PTMC 5000 -Et" and "PPFS-gS-PCL 3000 -OH" prepared according to example 5.

[0058] In the rest of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the limits are included, unless otherwise stated. Detailed description COMB POLYMER (i) PPFS type polymer intended to form the main chain of the comb polymer

[0059] As mentioned above, the comb polymer according to the invention is formed from a polymer obtained from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, and intended to form the main chain of the comb polymer.

[0060] The PPFS type polymer can be a homopolymer or a copolymer.

[0061] The monomers of the type 1-ethenyl-2,3,4,5,6-pentafluorobenzene, also more commonly called 2,3,4,5,6-pentafluorostyrene (PFS) and 1-allyl-2,3,4,5,6-pentafluorobenzene (IUPAC name 1,2,3,4,5-pentafluoro-6-prop-2-enylbenzene) correspond to the following formula (M1): in which e is 0 (case of pentafluorostyrene) or e is 1 (case of 1-allyl-2,3,4,5,6-pentafluorobenzene).

[0062] Preferably, the PPFS type polymer is a homopolymer.

[0063] For example, the PPFS-type polymer may be a poly(2,3,4,5,6-pentafluorostyrene) (PPFS) or a poly(1,2,3,4,5-pentafluoro-6-prop-2-enylbenzene), preferably a poly(2,3,4,5,6-pentafluorostyrene).

[0064] For the purposes of simplification, polymers derived from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, in particular of the poly(2,3,4,5,6-pentafluorostyrene) or poly(1,2,3,4,5-pentafluoro-6-prop-2-enylbenzene) type, are more simply referred to as “pentafluorostyrene-type polymer” or “PPFS-type polymer”.

[0065] The PPFS type polymer used to form the main chain of a comb polymer according to the invention advantageously has a number-average molar mass M n greater than or equal to 10,000 g.mol -1< , in particular between 10,000 g.mol -1< and 1,000,000 g.mol -1< , in particular between 40,000 g.mol -1< and 600,000 g.mol -1< , more particularly between 40,000 g.mol -1< and 400,000 g.mol -1< , or even between 50,000 g.mol -1< and 100,000 g.mol -1< .

[0066] The number-average molecular mass, also called number-average molar mass, of a PPFS-type polymer can be determined by size exclusion chromatography (SEC), preferably with TDS calibration.

[0067] In particular, the number-average degree of polymerization of the PPFS-type polymer, corresponding to the number of monomer units constituting the polymer, may be greater than or equal to 50, in particular between 50 and 4,200 and more particularly between 50 and 520.

[0068] According to a particular embodiment, the PPFS type polymer intended to form the main chain of a comb polymer according to the invention is a poly(2,3,4,5,6-pentafluorostyrene) (PPFS), in particular having a number-average molecular mass of between 10,000 g.mol -1< and 600,000 g.mol -1< and more particularly between 40,000 g.mol -1< and 100,000 g.mol -1<.

[0069] Preferably, the length of the PPFS type polymer, intended to form the main chain of the comb polymer according to the invention, in other words the degree of polymerization of the PPFS type polymer forming the main chain of the comb polymer according to the invention, is sufficiently high, so that the comb polymer formed according to the invention has a molar mass greater than the so-called critical entanglement molar mass.

[0070] The critical entanglement molar mass, denoted M c , for a given polymer, is generally defined as the mass from which the dynamics of the polymer is in a crawling regime. This critical entanglement molar mass can be determined empirically by methods known to those skilled in the art.

[0071] Controlling the average molecular mass of the comb polymer according to the invention makes it possible to control the mechanical properties of the comb polymer obtained, and in particular its viscoelasticity properties.

[0072] The comb polymer according to the invention is advantageously capable of forming a three-dimensional network, resulting from the entanglement of the polymer chains, and has a rubbery plateau identifiable for example by rheological measurements (for example, Young's modulus and shear modulus measured in multi-frequency dynamic mechanical analysis) on the polymer formed.

[0073] In a particular embodiment, the PPFS type polymer corresponds to the following formula (I): in which e is 0 or 1; s represents the number of monomeric units of the PPFS type polymer (corresponding to the degree of polymerization), in particular s is greater than or equal to 50, in particular between 50 and 4,200.

[0074] The PPFS type polymer used in the process according to the invention, intended to form the main chain of a comb polymer according to the invention, can be obtained beforehand by synthesis methods known to those skilled in the art. For example, it can be synthesized by a radical polymerization method, in particular by controlled radical polymerization, as described for example by Atanasov et al. [7].

[0075] Alternatively, it can be synthesized by Ziegler-Natta catalysis. Ziegler-Natta polymerization processes are well known for example for the synthesis of polystyrene [8]. They have been described in the case of the synthesis of PPFS in EP 3 763 748 A1 [9].

[0076] Advantageously, synthesis by Ziegler-Natta catalysis makes it possible to produce polymers with average molecular masses and adjustable dispersity, with good yields.

[0077] The PPFS type polymer can thus be formed by polymerization from the mixture of a Ziegler Natta type catalytic system comprising a catalyst and a co-catalyst; and 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers.

[0078] This synthesis method includes more specifically: bringing into contact a Ziegler Natta type catalytic system comprising a catalyst and a co-catalyst; with monomers of formula (M1) above; exposing the mixture thus formed to stirring and heating conditions conducive to the polymerization of said monomers.

[0079] The Ziegler-Natta type catalytic system can be of any generation, i.e. 1, 2, 3, 4 or later. Said catalytic system can be supported, homogeneous or heterogeneous.

[0080] The Ziegler Natta type catalytic system used for the synthesis of the PPFS type polymer can include: a catalyst containing a derivative, in particular a halide or an alcoholate, of a transition metal from group IV, V or VI of the periodic table of elements, preferably chosen from titanium, zirconium, vanadium, cobalt, chromium and nickel; and a co-catalyst containing a hydride or an alkyl derivative of an element from columns 1, 2 or 13 of the periodic table of elements, and preferably containing a hydride or an alkyl derivative of aluminium.

[0081] According to a particular variant of this embodiment, the catalyst containing a derivative of a transition metal from group IV, V or VI of the periodic table of elements is chosen from TiCl 4 , TiCl 3 , VCl 3 , VCl 4 , CoCl 2 , Ti(OBu) 4 and Cr(acac) 3 .

[0082] In particular, the co-catalyst containing a hydride or an alkyl derivative of an element from columns 1, 2 or 13 of the periodic table of elements is chosen from AlEt 3 , AlEt 2 Cl, AlEtCl, AlEtCl 2 , AlBu 3 , GaEt 3 and BeEt 2 . Preferably, according to this embodiment, the catalytic system is chosen from TiCl 4 / AlEt 3 , TiCl 3 / AlEt 2 Cl, TiCl 3 / GaEt 3 , TiCl 3 / BeEt 2 , VCl 4 / AlEt 2 Cl, CoCl 2 / AlEtCl, VCl 3 / AlEt 3 , Ti(OBu) 4 / AlEt 3 , Cr(acac) 3 / AlEt 3 , and even more preferably is TiCl 4 / AlEt 3 .

[0083] Such a Ziegler-Natta type catalytic system can be prepared, for example, by adding triethyl aluminum to titanium chloride and then allowing the mixture to stabilize for 30 minutes.

[0084] Alternatively, the Ziegler-Natta type catalytic system may comprise: TiCl 4 supported on MgCl 2 as catalyst; and AlEt 3 as co-catalyst.

[0085] Alternatively, the Ziegler Natta type catalytic system may comprise: a catalyst selected from metallocenes; and a co-catalyst selected from methylaluminoxane (MAO), Ph 3 C +< B(C 6 F 5 ) 4 -< and B(C 6 F 5 ) 3 .

[0086] Preferably, according to this embodiment, the catalytic system is chosen from ZrCp 2 Cl 2 / MAO, ZrCp 2 Cl 2 / B(C 6 F 5 ) 3 , ZrCp 2 Cl 2 / Ph 3 C +< B(C 6 F 5 ) 4 -< , CpTiCl 3 / MAO, and

[0087] According to a preferred embodiment, the catalyst / co-catalyst molar ratio is between 0.3 and 10, preferably between 0.5 and 2.

[0088] The contacting of a Ziegler-Natta type catalytic system, in particular as defined above, with the monomers of formula (M1) above can be carried out by simple mixing, in the presence or absence of a solvent such as fluorobenzene or tetrahydrofuran. The molar ratio of monomers (M1) / catalytic system can be between 10 and 1000, in particular between 10 and 250.

[0089] The mixture is then exposed to stirring and heating conditions conducive to the polymerization of the monomers (M1). In particular, the mixture may be exposed to a temperature level of between 60°C and 80°C, in particular for a period of at least 10 hours. Stirring may be carried out manually or mechanically, in particular using a conventional stirring device.

[0090] Preferably, the synthesis of the PPFS-type polymer is followed by a step of neutralization of the catalyst, for example with ethanol, then filtration of the catalytic system. The PPFS-type polymer thus formed can be precipitated, for example in methanol. (ii) Polycarbonate / polyester telechelic polymer intended to form the side chains of the comb polymer

[0091] As mentioned above, the formation of a comb polymer according to the invention uses at least one polymer, intended to form the side chains of the comb polymer, obtained from one or more cyclic monomers of five to eight members chosen from lactones and cyclic carbonates, and functionalized by at least one hydroxyl function at one of its ends, and a free thiol function, in particular at the other of its ends.

[0092] Preferably, a polymer intended to form the side chains of the comb polymer, obtained from one or more cyclic monomers of five to eight members chosen from lactones and cyclic carbonates, is functionalized by a single hydroxyl function at one of its ends, and a free thiol function at the other of its ends. Preferably, it is a linear polymer functionalized at each of its ends.

[0093] Generally speaking, the term "telechelic polycarbonate / polyester" will be used to designate a polymer intended to form the side chains of a comb polymer according to the invention, carrying at least one hydroxyl function and one free thiol function, preferably at each of the ends of said polymer.

[0094] The cyclic monomer(s) from which a polycarbonate / telechelic polyester polymer according to the invention is obtained more particularly correspond to the following formula (M2): in which: X represents a carbon atom or an oxygen atom; n 1 is 0 or is an integer between 1 and 3; said monomers being optionally substituted, on one or more of the carbon atoms of the cycle, by one or more substituents R 1 . The substituents of the cyclic monomer, R 1 , may be more particularly chosen from alkyl groups, in particular C 1 to C 5 , linear or branched.

[0095] According to a particular embodiment, the telechelic polymer intended to form the side chains of the comb polymer according to the invention is a telechelic polycarbonate, in other words it is obtained from monomers of the cyclic carbonate type with five to eight members.

[0096] Cyclic carbonates can more particularly be of the following formula (M3): in which m being an integer between 1 and 3, preferably m is 1 or 2, more preferably m is 2; x is 0 or is an integer between 1 and 2m+2; and R 1 , carried by one or more carbon atoms of the cycle, represent, independently of one another, substituents, in particular alkyl groups, in particular C 1 to C 5 , linear or branched.

[0097] Preferably, x is 0.

[0098] Examples of cyclic carbonate monomers include trimethylene carbonate and its derivatives, particularly trimethylene carbonate.

[0099] According to another particular embodiment, the polymer intended to form the side chains of the comb polymer according to the invention is a telechelic polyester, in other words is obtained from lactone type monomers.

[0100] By lactone, we mean more particularly monomers corresponding to the following formula (M4): in which n is an integer ranging from 1 to 3, in particular n is 2; y is 0 or is an integer between 1 and 2n+6; and R 1 , carried by one or more carbon atoms of the cycle, represent, independently of each other, substituents, in particular alkyl groups, in particular C 1 to C 5 , linear or branched. In particular, y is 0.

[0101] An example of a lactone monomer is ε-caprolactone.

[0102] Preferably, the telechelic polycarbonate / polyester is formed from one or more monomers selected from trimethylene carbonate and ε-caprolactone.

[0103] The telechelic polymers intended to form the side chains of the comb polymer according to the invention may be homopolymers or copolymers, in particular homopolymers, obtained from at least one cyclic monomer with five to eight members chosen from lactones and cyclic carbonates. According to the invention, the homopolymers or copolymers, in particular the homopolymers, obtained from at least one cyclic monomer with five to eight members chosen from lactones and cyclic carbonates, are designated under the general term "polycarbonate / polyester".

[0104] Preferably, the telechelic polymers intended to form the side chains of the comb polymer according to the invention may be homopolymers or copolymers, in particular homopolymers, obtained from one or more cyclic monomer(s) chosen from trimethylene carbonate and ε-caprolactone.

[0105] In particular, a telechelic polymer intended to form the side chains of the comb polymer according to the invention may be a telechelic poly(trimethylene carbonate) (PTMC) or poly(ε-caprolactone) (PCL), having at one of its ends a free thiol function and at the other of its ends at least one hydroxyl function, preferably a single hydroxyl function.

[0106] As indicated above, a telechelic polycarbonate / polyester polymer used according to the invention to form the side chains of the comb polymer has one or more hydroxyl functions at one of its ends, and a free thiol function. In a particular embodiment, said telechelic polycarbonate / polyester polymer used according to the invention has a hydroxyl function at one of its ends and a free thiol function at the other of its ends.

[0107] By free thiol function, we mean an unprotected -SH function, which can react by nucleophilic substitution with a fluorine function under the conditions described in the rest of the text.

[0108] The inventors have thus developed a method for synthesizing such telechelic polycarbonate / polyester polymers, in a single step, by ring-opening polymerization (or ROP for Ring-Opening Polymerization in English terminology) of one or more cyclic monomers as described previously, for example trimethylene carbonate and / or ε-caprolactone, in the presence of at least one initiator which is a mono or poly-alcohol carrying a free thiol function, in particular a monoalcohol carrying a free thiol function.

[0109] The synthesis of polyesters or polycarbonates by ring-opening polymerization under the action of a catalyst and an initiator comprising a hydroxyl function is well known. More particularly, ROP by the cationic route (

[10] -

[12] ) of PCL or PTMC has been proposed, for example by Makiguchi

[12] who uses, as organocatalyst, diphenyl phosphate (DPP) and a phenyl propanol type initiator and allows access to controlled polymerization, in particular a low polydispersity index (PI) and good control of the molar mass as a function of the initial monomer / initiator molar ratio. The polymerization involves almost exclusively the activated monomer mechanism, in other words, the initiation and propagation of the polymerization operate by reaction between the monomer and a hydroxyl function carried by the initiator or located at the end of the propagating chain.In fact, the nature of the linear chain ends is controlled, one of the ends having a hydroxyl function and the other end is dictated by the nature of the initiator, and therefore, in the case of a phenyl propanol type initiator, has a non-reactive character. 1,1' binaphthyl 2,2' diyl hydrogen phosphate (BNPH) has also been proposed as a catalyst, and has better activity than DPP

[13] .

[0110] Some studies have already reported the possibility of synthesizing a telechelic poly(caprolactone) with a thiol function on one end and a hydroxyl function on the other end. Zhu et al

[14] thus proposes a synthesis of a poly(caprolactone) using ytrium triphenylphosphate as a catalyst and mercapto hexan-1-ol as a polymerization initiator. The conditions used are such that 70 to 80% of the synthesized chains have a thiol function at one end and a hydroxyl function at the other, i.e. good "thiol fidelity". It has been shown that this chemoselectivity or "thiol fidelity" can be further increased when tin triflate

[15] is used as a catalyst or organic catalysts such as diphenyl phosphate (DPP)

[16] . To the inventors' knowledge, no study has yet proposed the synthesis of polycarbonate, for example PTMC, telechelic with a reactive thiol function, in particular at one of its ends.

[0111] The telechelic polycarbonate / polyester polymers used according to the invention to form the side chains are advantageously obtained by ROP of one or more cyclic monomers as described previously, for example trimethylene carbonate or ε-caprolactone, in the presence of at least one initiator which is a mono or poly-alcohol, in particular a mono-alcohol, carrying a free thiol function and a catalyst, preferably an organo-catalyst.

[0112] Preferably, the initiator used for the ROP synthesis of a telechelic polycarbonate / polyester according to the invention is a mercapto-alcohol, and more particularly a mercapto-alkanol, in particular of formula: [Chem 7] HS-(CH 2 ) q -CH 2 -OH, in which: q is 0 or is an integer between 1 and 10, in particular between 3 and 7, preferably is 5.

[0113] The initiator may be chosen, for example, from 4-mercaptobutan-1-ol, 5-mercaptopentan-1-ol, 6-mercaptohexan-1-ol and 7-mercaptoheptan-1-ol. For example, the initiator is 6-mercaptohexan-1-ol.

[0114] The catalyst used for the ROP reaction is preferably an organic catalyst or organocatalyst, such as, for example, diphenyl phosphate (DPP) or 1,1' binaphthyl 2,2' diyl hydrogen phosphate (BNPH). The catalyst is preferably used in a catalyst / initiator molar ratio of between 0.1 and 10, in particular between 0.25 and 1.

[0115] A person skilled in the art is able to adjust the operating conditions of the ROP reaction. The reaction can be carried out with stirring in a solvent medium, for example in one or more apolar and aprotic solvents, or in bulk.

[0116] Preferably, the reaction is carried out in one or more organic solvents, for example dichloromethane (DCM), or toluene. Advantageously, the organic solvent allows the dissolution of said monomer(s) and of the initiator. Preferably, the concentration of cyclic monomer in the organic solvent is between 10 and 1000 g / L, in particular between 100 and 330 g / L.

[0117] The synthesis can be carried out at a temperature between 20°C and 50°C. It can be carried out under reflux.

[0118] The reaction time can be between 5 hours and 5 days. It can be adapted depending on the nature of the cyclic monomer and the desired molar mass.

[0119] The polymerization reaction can be stopped by adding a base such as triethylamine (TEA) or by using an ion exchange resin. The synthesized telechelic polycarbonate / polyester can be recovered by precipitation in a solvent such as methanol.

[0120] Advantageously, the method described above for the synthesis of telechelic polycarbonates / polyesters used according to the invention allows good control of the polymerization, in particular of the molar mass and the polydispersity of the telechelic polycarbonates / polyesters obtained.

[0121] In particular, the molar mass of the telechelic polymers obtained can be adjusted by varying the molar ratio between the monomers and the initiator. According to a particular embodiment, said monomer(s) and said initiator are used in a monomer(s) / initiator molar ratio of between 1 and 1000, preferably between 1 and 200, in particular between 10 and 100, in particular between 20 and 100.

[0122] Preferably, the number-average molar mass of a telechelic polycarbonate / polyester intended to form the side chains of a comb polymer according to the invention is strictly greater than 2,000 g.mol -1< , in order to allow good control of the ends of the polycarbonate / polyester chains formed. In particular, the telechelic polycarbonate / polyester may have a number-average molar mass of between 2,000 g.mol -1< and 20,000 g.mol -1< and more particularly between 2,500 g.mol -1< and 10,000 g.mol -1< , in particular between 3,000 g.mol -1< and 7,500 g.mol -1< .

[0123] The number-average molecular mass can be determined by size exclusion chromatography (SEC), especially with universal calibration. Preferably, the number-average molecular mass of a telechelic polycarbonate / polyester is determined by 1< H NMR analysis.

[0124] Advantageously, the telechelic polycarbonates / polyesters obtained have a low polydispersity index, advantageously strictly less than 1.2, preferably between 1 and 1.1.

[0125] The polydispersity index, denoted IP, is equal to the ratio of the weight-average molar mass Mw to the number-average molar mass Mn. The weight-average molar mass can be determined by size exclusion chromatography, in particular with universal calibration, or by 1< H NMR. Preferably, the polydispersity index of a telechelic polycarbonate / polyester is determined by size exclusion chromatography (SEC), in particular with universal calibration.

[0126] Advantageously, the method for synthesizing telechelic polymers according to the invention makes it possible to achieve good chemoselectivity of the polymerization. The initiation and propagation of the polymerization will essentially involve a hydroxyl function carried by the initiator or located at the end of the chain during propagation. Consequently, at the end of the synthesis, at least 70% of the polymer chains formed, in particular at least 80%, are telechelic polymers according to the invention, in other words they have at least one free hydroxyl function at one of its ends, and a free thiol function, in particular at the other of its ends.

[0127] In a particular embodiment, the telechelic polycarbonate / polyester used according to the invention to form the side chains of a comb polymer according to the invention corresponds to the following formula (II): in which q is as defined previously for the mercapto-alkanol initiator, n 1 is 0 or is an integer between 1 and 3, X represents a carbon atom or an oxygen atom, and p represents the number of monomeric units of the telechelic polymer (corresponding to the degree of polymerization), in particular p is greater than or equal to 20, in particular between 20 and 200, more particularly between 24 and 100, or even between 31 and 75.

[0128] It is understood that X and n 1 may be identical or different for the p monomeric units of the telechelic polymer, the telechelic polymer thus being able to be a homopolymer of polycarbonate type, for example a PTMC, a homopolymer of polyester type, for example a poly(caprolactone) or even a copolymer formed from one or more distinct cyclic monomers chosen from lactones and cyclic carbonates. Preferably, X and n 1 are identical for the p monomeric units of the telechelic polymer.

[0129] In a particular embodiment, the telechelic polymer is a telechelic polycarbonate of the following formula (II-a): in which q, p and n 1 are as defined previously.

[0130] In another particular embodiment, the telechelic polymer may be a polyester of the following formula (II-b): in which q, p and n 1 are as defined previously.

[0131] According to a particular embodiment, the telechelic polymer used to form the side chains of a comb polymer according to the invention is a poly(trimethylene carbonate) having at one of its ends a free thiol function and at the other of its ends at least one hydroxyl function, preferably a single hydroxyl function. According to another particular embodiment, the telechelic polymer used to form the side chains of a comb polymer according to the invention is a poly(ε-caprolactone), having at one of its ends a free thiol function and at the other of its ends at least one hydroxyl function, preferably a single hydroxyl function. (iii) Obtaining the comb polymer

[0132] As mentioned above, the comb polymer according to the invention is obtained by grafting the chains of said polycarbonate / telechelic polyester polymer(s) onto the PPFS type polymer. More particularly, obtaining the comb polymer involves grafting the polycarbonate / telechelic polyester polymers, in particular as described above, in position para of a part of the pentafluorophenyl groups of the monomeric units of the PPFS type polymer.

[0133] It is understood that the method may implement one or more distinct telechelic polymers, leading to identical or different side chains on the PPFS type polymer. Preferably, the method of the invention implements a single telechelic polymer, in particular as described above.

[0134] The grafting of the side chains onto the PPFS type polymer is more particularly carried out by nucleophilic substitution between the thiol function carried by the telechelic polymer and a fluorine atom in position para of a pentafluorophenyl group of the PPFS type polymer.

[0135] This nucleophilic substitution reaction is regioselective, meaning that only the fluorine atom in position para of a pentafluorophenyl group is substituted. Such a nucleophilic substitution reaction between a fluorine atom and a thiol function has for example been described for the grafting of a perfluorinated decanethiol or a mercapto-propanoic or mercapto-acetic acid onto a PPFS type polymer [17,18].

[0136] The nucleophilic substitution reaction for the grafting of the telechelic polymers according to the invention is more particularly carried out in the presence of a base. Advantageously, it is carried out in the presence of an aprotic base weaker than sodium hydride (NaH), sodium hydroxide (NaOH) and potassium hydroxide (KOH), preferably an aprotic base having a pKa strictly less than 15 and strictly greater than 10, in particular strictly less than 14, more particularly less than or equal to 13 and strictly greater than 10, or even between 10.2 and 13.

[0137] Advantageously, the nucleophilic substitution reaction for the grafting of telechelic polycarbonates / polyesters is carried out in the presence of a base chosen from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, or IUPAC name 2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine), triethylamine (TEA) and potassium carbonate (K 2 CO 3 ), in particular chosen from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and triethylamine (TEA). More preferably, the base is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).

[0138] In particular, the base can be implemented in a base / telechelic polymer molar ratio of between 0.1 and 1.

[0139] The substitution reaction for grafting telechelic polycarbonate / polyester polymers onto the PPFS-type polymer can be carried out more particularly in a solvent medium. The solvent medium makes it possible to solubilize the PPFS-type polymer and the telechelic polycarbonate / polyester. It can be formed from one or more polar aprotic solvent(s), in particular chosen from tetrahydrofuran (THF), amides such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP); methyl ethyl ketone (MEK), N-methyl-2-pyrrolidone and mixtures thereof, preferably in tetrahydrofuran (THF), N,N-dimethylformamide (DMF) or methyl ethyl ketone (MEK), more preferably methyl ethyl ketone (MEK).

[0140] The process of the invention allows a great variability in the rate of grafting in side chains of the comb polymer obtained.

[0141] The grafting rate can be more particularly adjusted by varying the molar ratio between the thiol functions present on the telechelic polycarbonate / polyester chains and the monomeric units of the PPFS-type polymer. In particular, said telechelic polymer(s) and said PPFS-type polymer can be implemented in a molar ratio of telechelic polymers / monomeric units of the PPFS-type polymer of between 0.1 and 1.

[0142] Advantageously, the molar grafting rate of the polycarbonate / polyester type side chains can thus be greater than or equal to 1% and less than or equal to 100%, in particular be between 5% and 90%, more particularly between 5% and 75%, or even between 10% and 60%. Advantageously, the grafting rate can be strictly greater than 35%, in particular be between 38% and 75% and more particularly between 40% and 60%.

[0143] The molar grafting rate is defined as the percentage of PPFS-type main chain repeat units with side chains. The molar grafting rate can be characterized by fluorine F 19< nuclear magnetic resonance (NMR). It can also be characterized by CES.

[0144] The substitution reaction may be carried out at a temperature between 10°C and 100°C, in particular between 15°C and 40°C, preferably between 20°C and 30°C, for example at room temperature. The reaction time may be between 3 hours and 48 hours, in particular between 6 hours and 24 hours, more particularly between 10 hours and 20 hours.

[0145] Preferably, the reaction medium is kept stirring during the grafting reaction.

[0146] After grafting, the synthesized comb polymer can be recovered by precipitation in a solvent such as ethanol. Comb polymer

[0147] At the end of the grafting step, the PPFS type polymer thus has polycarbonate / polyester chains originating from said telechelic polycarbonate / polyester(s) linked in position para of a part of the pentafluorophenyl groups via thioether bonds. Comb polymer purification

[0148] The comb polymer obtained after grafting (iii) the polycarbonate / polyester chains onto the PPFS type main chain can be subjected to one or more subsequent purification steps.

[0149] Advantageously, the purification of the comb polymer according to the invention is carried out by solubilization of the polymer obtained at the end of step (iii) of grafting the side chains in an organic solvent, then by precipitation of the comb polymer in a mixture of a first solvent chosen from methanol, ethanol, diethyl ether and their mixtures and a second solvent chosen from dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) and their mixtures, followed by a liquid / solid separation, for example filtration, and drying (evaporation of the solvents). In particular, said first solvent and said second solvent are miscible.

[0150] The solubilization solvent of the comb polymer may be, for example, dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF) or mixtures thereof, in particular dichloromethane.

[0151] Preferably, the polymer is precipitated in a mixture of acetone and methanol, the person skilled in the art being able to adjust the acetone / methanol volume ratio. In particular, the acetone / methanol volume ratio may be between 20 / 80 and 90 / 10, more particularly between 40 / 60 and 80 / 20, in particular between 50 / 50 and 70 / 30, or even between 55 / 45 and 65 / 35.

[0152] Surprisingly, as illustrated in examples, the inventors have shown that such a purification protocol advantageously makes it possible to eliminate ungrafted polycarbonate / polyester chains.

[0153] Preferably, the purification of the comb polymer according to the invention is carried out by solubilization of the polymer obtained at the end of step (iii) of grafting the side chains in dichloromethane, then by precipitation of the comb polymer in an acetone / methanol mixture, followed by liquid / solid separation, for example filtration, and drying (evaporation of the solvents).

[0154] Protection of the hydroxyl chain ends of the comb polymer

[0155] In a particular embodiment, the hydroxyl functions present at the ends of the side polycarbonate / polyester chains of the comb polymer may be in protected (or “capped”) form.

[0156] The process for preparing a comb polymer according to the invention can thus further comprise a step of protecting the hydroxyl functions present at the ends of the side polycarbonate / polyester chains of said comb polymer, by reaction with at least one compound, called a protective agent, as described in the rest of the text.

[0157] The protection of the hydroxyl functions can be carried out more particularly at the end of the synthesis of the comb polymer, preferably after purification as described above.

[0158] The formation of capped hydroxyl ends (more generally referred to as “end-capped” in English terminology) advantageously makes it possible to increase the electrochemical stability of the solid electrolyte formed from said comb polymer(s), the terminal hydroxyl functions being sensitive to reduction and oxidation, and likely to degrade upon contact with lithium salts.

[0159] A hydroxyl function is more particularly protected by forming a more chemically and electrochemically stable function. For example, the protection of hydroxyl functions can be more particularly carried out by reacting said hydroxyl function at the end of the chain with at least one compound, called a protective agent, chosen from acyl chlorides, for example benzoyl chloride, acetyl chloride, etc.; acid anhydrides, for example acetic anhydride, etc., and isocyanates such as p-toluenesulfonyl isocyanate, etc.

[0160] The protection of the hydroxyl functions can be carried out by directly adding said protective agent(s) to the reaction medium obtained at the end of the synthesis of the comb polymer in step (iii) or subsequently in a purification step as described previously, of the comb polymer.

[0161] A person skilled in the art is able to adjust the operating conditions to achieve the protection of the hydroxyl function(s) of the ends of the side chains of the comb polymer according to the invention. An example of a procedure for the protection of the hydroxyl functions using acetyl chloride is for example illustrated in the example section which follows.

[0162] The invention thus relates to a comb polymer, in particular as obtained at the end of the process of the invention described above, comprising a main chain of PPFS type formed from 1-ethenyl- and / or 1-allyl- 2,3,4,5,6-pentafluorobenzene monomers, a portion of the monomeric units of the main chain carrying polymeric side chains, called polycarbonate / polyester chains, formed from at least one cyclic monomer of five to eight members chosen from lactones and cyclic carbonates; said side polymeric chains being grafted in para pentafluorophenyl groups via thioether bonds.

[0163] The characteristics described above in the context of the process for preparing the comb polymer, in particular for the PPFS type polymer forming the main chain of the comb polymer and for the said polyester / polycarbonate polymer(s) intended to form the side chains, also apply to the comb polymer according to the invention.

[0164] In particular, the comb polymer according to the invention preferably has a main chain of PPFS type having a number-average molar mass M n greater than or equal to 10,000 g.mol -1< , in particular less than or equal to 1,000,000 g.mol -1< , in particular less than or equal to 600,000 g.mol -1< and more particularly between 40,000 g.mol -1< and 400,000 g.mol -1< , in particular between 50,000 g.mol -1< and 100,000 g.mol -1< .

[0165] The polycarbonate / polyester type side chains more particularly have a number-average molar mass strictly greater than 2,000 g.mol -1< , and in particular less than or equal to 20,000 g.mol -1< , in particular between 2,500 g.mol -1< and 10,000 g.mol -1< and more particularly between 3,000 g.mol -1< and 7,500 g.mol -1< .

[0166] As previously indicated, the side chains advantageously exhibit low polydispersity. In particular, the polydispersity index, the ratio of the weight-average molar mass Mw to the number-average molar mass Mn, is strictly less than 1.2.

[0167] Advantageously, as indicated previously, the process for obtaining a comb polymer according to the invention allows great latitude in terms of variation of the grafting rate of the side chains.

[0168] The molar grafting rate of the polycarbonate / polyester type side chains may thus be greater than or equal to 1% and less than or equal to 100%, in particular be between 5% and 90%, more particularly between 5% and 75%, or even between 10% and 60%. In a particular embodiment, the grafting rate may be strictly greater than 35%, in particular be between 38% and 75% and more particularly between 40% and 60%.

[0169] The polycarbonate / polyester side chains preferably have hydroxyl functions at the chain end, in protected or capped form, resulting from the reaction of said hydroxyl function with a protecting agent, as described previously.

[0170] In a particular embodiment, the monomeric units of the comb polymer according to the invention carrying a side chain, in particular obtained according to the process described previously, can thus be of the following formula (III): in which e, q, X, n 1 and p are as defined previously, said hydroxyl function at the end of the chain possibly being in protected form, for example in the -OAc form (Ac representing an acetyl group).

[0171] In a particularly preferred embodiment, the comb polymer comprises side chains of the same nature, in other words resulting from the grafting of a single telechelic polycarbonate / polyester at the level of the PPFS type polymer.

[0172] In a particular embodiment, the comb polymer obtained according to the invention is of formula (IV): in which e, p, q, n 1 and X are as defined previously; said hydroxyl functions at the ends of the side chains being optionally protected, as described previously; g corresponds to the average number of monomeric units carrying polymeric side chains; m corresponds to the average number of ungrafted monomeric units; with g / g+m representing the molar grafting rate in polymeric side chains, being in particular greater than or equal to 0.01, in particular between 0.05 and 1, in particular between 0.05 and 0.75, more particularly strictly greater than 0.35; the order of succession of the two types of monomeric units forming the polymer of formula (IV) being completely random. PREPARATION OF SOLID ELECTROLYTE

[0173] As mentioned above, the comb polymers according to the invention, in particular obtained by the process according to the invention, preferably after protection of the hydroxyl functions at the ends of the side polycarbonate / polyester chains, can be used, in combination with at least one ionic salt, to form a solid electrolyte, in particular in an electrochemical system, in particular in a lithium battery.

[0174] The solid electrolyte can be a solid polymer electrolyte (also called SPE for “Solid Polymeric Electrolyte” in Anglo-Saxon terminology) or a hybrid solid electrolyte (HSE for “Hybrid Solid Electrolyte” in Anglo-Saxon terminology).

[0175] The electrolyte formed according to the invention may be in any suitable form, in particular in the form of a film or a membrane.

[0176] In particular, the polymer network formed from the comb polymers according to the invention, in particular obtained by the process according to the invention, forms more than 50% by mass, in particular more than 75% by mass, of the total mass of said solid electrolyte.

[0177] Advantageously, the solid polymeric electrolyte film according to the invention is free from plasticizing agents, such as carbonates, for example ethylene carbonate or diethyl carbonate.

[0178] In particular, the solid electrolyte film according to the invention is distinct from a gel-type electrolyte, comprising a majority quantity of plasticizer.

[0179] The preparation of a solid electrolyte from the comb polymers according to the invention more particularly implements at least the following steps: (a) mixing, in the presence or absence of a solvent medium, of at least: one or more comb polymers according to the invention, as described previously, in particular obtained by the process according to the invention, at least one alkali or alkaline-earth metal salt, in particular a lithium salt; and optionally, in particular in the case of the preparation of an HSE, at least one inorganic filler; (b) formation, in particular on the surface of a substrate, of a solid electrolyte from said mixture.

[0180] The alkali or alkaline earth metal salt is used with the comb polymer according to the invention to ensure the conduction of the ions.

[0181] In the context of the invention, the following terms are understood to mean: “alkali metals”, the chemical elements of the first column of the periodic table of elements, and more particularly chosen from lithium, sodium, potassium, rubidium, cesium. Preferably, the alkali metal is lithium, sodium or potassium, and more preferably lithium; “alkaline earth metals”, the chemical elements of the second column of the periodic table of elements, and more particularly chosen from beryllium, magnesium, calcium, strontium, barium, radium. Preferably, the alkaline earth metal is magnesium or calcium.

[0182] The salt of an alkali metal may be, for example, a lithium salt or a sodium salt; the salt of an alkaline earth metal may be, for example, a magnesium salt.

[0183] Examples of lithium salts include LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiCF 3 SO 3 , LiN(C 2 F 5 SO 2 ) 2 , lithium bistrifluoromethylsulfonylimide LiN[SO 2 CF 3 ] 2 (known as LiTFSI), lithium bis(fluorosulfonyl)amide (known as LiFSI) LiN[SO 2 F] 2 , lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (known as LiTDI), lithium bispentafluoroethylsulfonylimide (known as LiBETI), lithium bis(oxalato)borate (known as LiBOB) and lithium difluoro(oxalato)borate (known as abbreviation LiFOB) and mixtures thereof.

[0184] Preferably, the electrolyte comprises, as lithium salt, LiTFSI or LiFSI, preferably LiTFSI.

[0185] It is up to the person skilled in the art to adjust the quantity of alkali or alkaline earth metal salts, in particular with regard to the nature of the comb polymer, and in particular the nature of the side polycarbonate / polyester chains carried by the comb polymer, used according to the invention.

[0186] According to a particular embodiment, the quantities of comb polymer(s) and lithium salt(s) are adjusted so that the molar ratio between the carbonyl groups of the polycarbonate / polyester side chains (in other words CO 3 groups in the case of polycarbonate chains, and CO 2 groups in the case of polyester chains) relative to the lithium, noted [CO] / [Li +< ], is between 0.1 and 30, in particular between 0.5 and 20 and more particularly between 5 and 15.

[0187] According to a first embodiment variant, said comb polymer(s) according to the invention are used to form a solid polymer electrolyte (SPE), the preparation of said electrolyte comprising the mixture of at least one comb polymer according to the invention and of which the terminal hydroxyl functions are optionally protected, and at least one alkali or alkaline-earth metal salt, for example a lithium salt.

[0188] According to another embodiment variant, said comb polymer(s) according to the invention are used to form a hybrid solid electrolyte (HSE), the preparation of said electrolyte then comprising the mixture of at least one comb polymer according to the invention and whose terminal hydroxyl functions are protected, of at least one alkali or alkaline-earth metal salt, for example a lithium salt and, in addition, of at least one inorganic filler.

[0189] The inorganic fillers may be chosen from inorganic fillers which conduct alkali or alkaline-earth cation(s), in particular which conduct lithium ions, non-conductive fillers which conduct alkali or alkaline-earth cation(s), and mixtures thereof.

[0190] The lithium ion conductive fillers can be chosen, for example, from lithiated oxides, such as Li 7 La 3 Zr 2 O 12 (LLZO) and Li 0.33 La 0.56 TiO 3 (LLTO), Li 13 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), etc.

[0191] These may also be charges chosen from: garnets, for example chosen from Li 7 La 3 Zr 2 O 12 , Li 6 La 2 BaTa 2 O 12 , etc.; lithiated phosphates, for example chosen from Li 3 PO 4 , LiPO 3 , etc.; lithiated borates, for example chosen from Li 3 BO 3 , etc.; oxynitrides, for example chosen from Li 3 PO 4-x N 2x / 3 , Li 4 SiO 4-x N 2x / 3 , Li 4 GeO 4-x N 2x / 3 with 0 <x<4 ou Li 3 BO 3-x N 2x / 3 avec 0<x<3 ; les composés lithiés à base d'oxynitrure de lithium et de phosphore (appelés LiPON) ; les silicates, par exemple Li 2 Si 2 O 5 ; les sulfurés, par exemple l'argyrodite.

[0192] Non-conductive fillers of alkali or alkaline-earth cations can for example be chosen from alumina (Al 2 O 3 ), silica (SiO 2 ), titanium dioxide (TiO 2 ) etc.

[0193] Said inorganic filler(s) may be used in a filler(s) / polymer(s) comb volume ratio of between 1 / 99 and 80 / 20, in particular between 20 / 80 and 80 / 20, more particularly between 20 / 80 and 60 / 40.

[0194] The mixing of said comb polymer(s) according to the invention, said alkali or alkaline-earth metal salt(s) and, optionally, said inorganic filler(s), is more particularly carried out under conditions allowing good dispersion of said alkali or alkaline-earth metal salt(s) and, optionally, of said inorganic filler(s), at the level of the comb polymers according to the invention. The mixing can be carried out in the presence or absence of a solvent.

[0195] The preparation of a solid electrolyte film according to the invention can thus be carried out either by the route using a solvent medium (called "solvent route"), or by the route using the polymer in the molten state, in the absence of solvent (called "dry route" or "molten route"). According to a first embodiment variant, the solid electrolyte film is prepared by the "solvent" route. In the context of this variant, the mixture of said comb polymer(s) according to the invention, of said alkali or alkaline-earth metal salt(s) and, optionally, of said inorganic filler(s), is more particularly carried out in a solvent medium. The solvent medium can be formed from one or more polar organic solvents. By way of examples, they can be chosen from acetone, tetrahydrofuran (THF), acetonitrile and mixtures thereof.

[0196] Preferably, the mixture is heated to a temperature below 100°C. In particular, the mixture is carried out at a temperature greater than or equal to 25°C, in particular between 40 and 60°C.

[0197] The solid electrolyte may be formed by depositing said mixture on the surface of a substrate, for example by coating, followed by evaporation of said solvent(s), in particular to obtain a “dry” electrolyte or film.

[0198] In particular, said solvent(s) may be evaporated under vacuum at a temperature of between 70°C and 90°C, in particular approximately 80°C.

[0199] By "dry" is meant that the solid electrolyte or solid electrolyte film comprises less than 0.1% by mass of solvent, in particular less than 0.05% by mass and more particularly less than 0.02% by mass of solvent.

[0200] According to another embodiment, the solid electrolyte, in particular in the form of a film, is prepared in the absence of solvent, by the “melt” route, in particular by extrusion.

[0201] In the context of this embodiment variant, the molten mixture may more particularly be carried out by heating to a temperature greater than Tg + 30°C, where Tg is the glass transition temperature of the comb polymer. In particular, the mixture is carried out at a temperature greater than or equal to - 0°C, in particular between 20°C and 80°C.

[0202] The molten mixture can then be formed into a film, supported by a substrate or self-supported, by any melt extrusion technique known to those skilled in the art.

[0203] As mentioned above, the solid electrolyte can be prepared in the form of an electrolyte film or membrane directly on the surface of a suitable substrate, in particular an inert one.

[0204] The substrate can be of various types. It can be made of glass, alumina, silicone, polyimide, polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), silicone, polypropylene or even stainless steel.

[0205] The solid electrolyte film can optionally be detached from the substrate to be implemented at the level of the electrochemical system for which it is intended, in particular transferred onto at least one electrode.

[0206] The solid electrolyte film may have, for example, a thickness of between 20 and 500 µm, in particular between 20 and 100 µm and more particularly between 40 and 60 µm. ELECTROCHEMICAL SYSTEM

[0207] The solid electrolyte obtained according to the invention, in particular of the SPE or HSE type, can be advantageously used as a solid electrolyte in an electrochemical system. The invention also relates, according to another of its aspects, to an electrochemical system comprising a solid electrolyte, in particular a solid electrolyte film according to the invention, in particular acting both as an ionic conductor and as a separator between the positive and negative electrodes.

[0208] The electrochemical system may be a generator, converter or electrochemical storage system. More specifically, it may be a fuel cell, for example a primary or secondary battery, for example a lithium, sodium, magnesium, potassium or calcium battery; a flow battery ("redox flow battery" in English terminology); a lithium-air or lithium-sulfur accumulator.

[0209] According to a particular embodiment, the solid electrolyte is implemented in a rechargeable battery, in particular in a lithium battery, in particular a lithium-ion or lithium-metal battery.

[0210] The solid electrolyte according to the invention can be more particularly implemented as a separator electrolyte within an electrochemical system. The term "separator electrolyte" means a film of solid electrolyte positioned between the positive and negative electrodes of an electrochemical system, and acting both as an ionic conductor and separator between the positive and negative electrodes.

[0211] In particular, the invention also relates, according to another of its aspects, to an electrode / electrolytic membrane assembly, comprising a solid electrolyte membrane according to the invention.

[0212] An electrochemical system according to the invention generally comprises at least one positive electrode and one negative electrode between which there is a solid electrolyte film acting both as an ionic conductor and separator between the positive and negative electrodes.

[0213] The positive electrode of a lithium battery generally comprises, as electrochemically active material, lamellar compounds, such as LiCoO 2 , LiNiO 2 and mixed Li(Ni, Co, Mn, Al)O 2 , or compounds of spinel structure of compositions close to LiMn 2 O 4 , lithium phosphates, in particular LiMnFePO 4 or LiFePO 4 .

[0214] Advantageously, the positive electrode comprises, as electrochemically active material, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 (NCM cathodes) or LiCoO 2 , preferably LiNi 1 / 3 Mn 1 / 3 CO 1 / 3 O 2 .

[0215] The negative electrode generally comprises, as electrochemically active material, lithium metal or lithium-based alloy in the case of primary accumulators, or intercalation materials such as graphite carbon, or lithiated titanium oxide (Li 4 Ti 5 O 12 ) or titanium and niobium oxide (TiNb 2 O 7 ), in the case of accumulators based on lithium-ion technology.

[0216] Advantageously, it may be a lithium-metal battery, comprising a lithium metal electrode Li 0 < and an electrode comprising LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 or LiCoO 2 , preferably LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 .

[0217] The invention will now be described by means of the following examples and figures, given of course for illustrative purposes and not as a limitation of the invention. Example 1 Preparation of a poly(2,3,4,5,6-pentafluorostyrene) (PPFS) intended to form the main chain of a comb polymer according to the invention 1.1 Synthesis of a PPFS by bulk polymerization under Ziegler Natta catalysis ("PPFS-03") Preparation of a Ziegler Natta catalyst solution:

[0218] In a glove box, 1.2 mL of TiCl 4 (1 equivalent) and 15 mL of anhydrous toluene are added to a 100 mL two-necked flask topped with a dropping funnel. 1.9 mL of AlEt 3 (1.2 equivalents) and 15 mL of toluene are added to the addition funnel. The assembly is removed from the glove box and the bottom of the two-necked flask is immersed in an ice bath; the AlEt 3 solution is added dropwise to the TiCl 4 solution, with vigorous stirring. The ice bath is removed at the end of the addition and the reaction mixture is kept stirring for 30 min at room temperature. The Ziegler Natta catalyst solution is ready for use. Polymerization of PPFS:

[0219]

[0220] 75 mL of 2,3,4,5,6-pentafluorostyrene (PFS; 50 equivalents) are introduced into a 500 mL two-necked flask. The assembly is placed under argon flow. 25 mL of Ziegler Natta catalyst solution are added to the two-necked flask. The reaction medium is stirred and heated at 70°C for 4 h, then at 120°C for 36 h. At the end of polymerization, a black solid is obtained at the bottom of the flask.

[0221] The solid is solubilized in fluorobenzene and then the synthesized poly(2,3,4,5,6-pentafluorostyrene) (PPFS) is purified by precipitation in MeOH. After filtration, the PPFS (white powder) is dried under vacuum at 60°C for 48 hours.

[0222] 69.8 g of PPFS, named "PPFS-03", are obtained with a mass yield of approximately 93%.

[0223] The obtained polymer is characterized by nuclear magnetic resonance (NMR) of 1< H and 19< F ( Figure 1 ): NMR 19< F (400 MHz; CDCl 3; 298 K): δ ppm: -143ppm (m, 2F orto) ; -154ppm (s, 1F para ) ; -161ppm (s, meta ) .

[0224] The number-average molar mass Mn, determined by Size Exclusion Chromatography (CES (THF, 30°C, TDS calibration)) ( Figure 2 ) is 53 kg / mol with a polydispersity index, IP = M w / M n , of 2.2. 1.2 Synthesis of a PPFS by radical emulsion polymerization ("PPFS-Em-01")

[0225]

[0226] 30 mL of distilled water and 0.3 g of SDS (sodium dodecyl sulfate, 2% by mass of PFS) are introduced into a mini-reactor. The medium is stirred and heated to 75°C for 30 min. 15 g of PFS are introduced into the reactor. 15 min after the addition, 0.17 g of ammonium persulfate (1.1% by mass of PFS), dissolved in 15 mL of distilled water, are added to the mini-reactor. The medium is kept stirring and heated to 75°C for 3 h and then to 85°C for 1 h. A white latex is obtained.

[0227] The latex is precipitated in ethanol and then filtered. The product is dried at 60°C under vacuum for 48 hours.

[0228] 10.8 g of PPFS, named PPFS-Em-01, are obtained with a mass yield of approximately 72%.

[0229] The number-average molar mass Mn determined by CES (THF, 30°C, TDS calibration) ( Figure 3 ) is 280 kg / mol with a polydispersity index, IP = M w / M n , of 1.9.

[0230] The polymer is also characterized by nuclear magnetic resonance (NMR) of 1< H and 19< F ( Figure 4 ). Example 2 Preparation of a telechelic poly(trimethylene carbonate) (PTMC) intended to form the side chains of a comb polymer according to the invention 2.1. Synthesis of a telechelic PTMC ("SH-PTMC-OH-01")

[0231]

[0232] 150 g of trimethylene carbonate (TMC; 50 equivalents) are introduced into a two-necked flask containing a magnetic stirrer. The two-necked flask is attached to a condenser. The assembly is evacuated and then under argon flow. 1.4 L of anhydrous toluene are added to solubilize the TMC. 7.35 g of diphenyl phosphate (DPP) (1 equivalent) are weighed into a flask and then solubilized in 100 mL of anhydrous toluene. The DPP solution in toluene is added to the two-necked reaction flask. 3.95 mL (1 equivalent) of 6-mercaptohexan-1-ol are then added to the reaction medium. The reaction medium is kept stirring at room temperature for 30 h. After this time, 3.1 mL (1.05 equivalents) of triethylamine (TEA) are added to the reaction medium to stop the polymerization. The reaction medium is concentrated, then precipitated in methanol (MeOH). The product, in the form of a viscous polymer, is recovered and dried at 60°C for 48 hours.

[0233] Approximately 140 g of PTMC, named "SH-PTMC-OH-01", are obtained with a mass yield of 90%.

[0234] The polymer is characterized by nuclear magnetic resonance (NMR) of 1< H ( Figure 5 ): 1< H NMR (400 MHz; CDCl3; 298 K): δ ppm 4.25 (t, 2H); 4.20 (t, 2nx2H); 4.09 (t, 2H); 3.69 (t, 2H); 2.49 (q, 2H); 2.01 (m, nx2H); 1.88 (m, 4H), 1.64-1.59 (m, 4H); 1.37-1.3 (m, 5H). It can be deduced from the NMR spectrum that the control of chemoselectivity is such that 85% of the PTMC chains obtained are initiated by 6-mercaptohexan-1-ol. The number-average molar mass Mn, obtained from 1< H NMR analysis, is 3700 g / mol. The polydispersity index, deduced from CES analysis (THF, 30°C, universal calibration), IP = M w / M n , is 1.09 ( Figure 6 ). 2.2. Synthesis of a telechelic PTMC ("SH-PTMC-OH-02")

[0235] 250 g of TMC (75 equivalents) are introduced into a two-necked flask containing a magnetic stirrer. The two-necked flask is fixed on a condenser. The assembly is placed under vacuum and then under a flow of argon. 1.4 L of anhydrous dichloromethane (DCM) are added to solubilize the TMC. 8.25 g of diphenyl phosphate (DPP) (1 equivalent) are weighed into a flask and then solubilized in 100 mL of anhydrous DCM. The DPP solution in DCM is added to the two-necked reaction flask. 4.5 mL (1 equivalent) of 6-mercaptohexan-1-ol are then added to the reaction medium. The reaction medium is refluxed with DCM (40°C) for 30 h. After this time, 3.6 mL (1.02 equivalents) of triethylamine (TEA) are added to the reaction medium to stop the polymerization. The reaction medium is concentrated, then precipitated in methanol (MeOH). The product, in the form of a viscous polymer, is recovered and dried at 60°C for 48 h.

[0236] Approximately 231 g of PTMC, named "SH-PTMC-OH-02", are obtained with a mass yield of 92%.

[0237] The polymer is characterized by nuclear magnetic resonance (NMR) of 1< H ( Figure 7 ).

[0238] It can be deduced from the NMR spectrum (CDCl3, 298K, 400MHz) that the control of chemoselectivity is such that 85% of the obtained PTMC chains are initiated by 6-mercaptohexan-1-ol. The number-average molar mass Mn, obtained from 1< H NMR analysis, is 5500 g / mol.

[0239] The polydispersity index, deduced from the CES analysis (THF, 30°C, universal calibration), IP = M w / M n , is 1.1. Example 3 Preparation of a poly(2,3,4,5,6-pentafluorostyrene) comb polymer carrying poly(trimethylene carbonate) grafts (PPFS-gS-PTMC)

[0240] 3.1. Synthesis of a comb copolymer PPFS-g 0.5 -S-PTMC 3700 -OH ("PPFS-gS-PTMC-OH-01")

[0241] In a 2 L two-necked flask, 94 g of SH-PTMC-OH-01 synthesized in Example 2.1 (0.75 equivalent; Mn ≈ 3700 g / mol) and 6.9 g of PPFS-03 synthesized in Example 1.1 (1 equivalent) are solubilized in 1.1 L of methyl ethyl ketone (MEK). After solubilization of PTMC and PPFS, 1.6 mL of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU; 0.3 equivalent) is added to the medium. The reaction medium is stirred for 16 h at room temperature. After this reaction time, the reaction medium is directly precipitated in ethanol. A transparent viscous polymer is obtained after drying.

[0242] In order to remove the PTMC chains not grafted on the PPFS, the product is solubilized in DCM and precipitated in an acetone / MeOH mixture (60:40). A transparent, purified viscous polymer is obtained after drying. It is named "PPFS-gS-PTMC-OH-01".

[0243] The obtained polymer is characterized by nuclear magnetic resonance (NMR) of 1< H (CDCl 3 , 298K, 400MHz) ( figure 8 ) and 19< F (CDCl 3, 298K, 400MHz) ( figure 9 ) and by CES (THF, 30°C, TDS calibration)) ( Figure 10 ).

[0244] The elimination of non-grafted PTMC chains on PPFS is confirmed by CES.

[0245] The molar grafting rate of PTMC chains on PPFS repeat units is estimated by 19< F NMR and / or CES at 50%. 3.2. Synthesis of the comb polymer PPFS-g 0.1 -S-PTMC 5500 -OH ("PPFS-gS-PTMC-OH-02")

[0246] In a 2L two-necked flask, 206 g of SH-PTMC-OH-02 synthesized in Example 2.2 (0.5 equivalent; Mn ≈ 5500 g / mol) and 11.9 g of PPFS-03 synthesized in Example 1.1 (1 equivalent) are solubilized in 1 L of MEK. After solubilization of the PTMC and PPFS, 3.9 mL of DBU (0.4 equivalent) is added to the medium. The reaction medium is stirred for 16 h at room temperature.

[0247] After this reaction time, the reaction medium is directly precipitated in an acetone / MeOH mixture (65:35) to remove the PTMC chains that have not reacted with the PPFS. A transparent, purified viscous polymer is obtained after drying. It is named "PPFS-gS-PTMC-OH-02".

[0248] The obtained polymer is characterized by nuclear magnetic resonance (NMR) of 1< H (CDCl 3 , 298K, 400MHz) ( Figure 11 ) and 19< F and by CES (THF, 30°C, TDS calibration)) ( Figure 12 ).

[0249] The elimination of ungrafted PTMC chains on PPFS is confirmed by CES. It is confirmed by 1< H NMR that the molar mass of PTMC chains is not modified during grafting.

[0250] The molar grafting rate of PTMC chains on PPFS repeat units is estimated by 19< F NMR and / or CES at 40%. 3.3. Protection of side chain ends (-OH)

[0251] The hydroxyl functions of the side chains of the PPFS-gS-PTMC-OH-01 copolymer synthesized in Example 3.1 can be protected, for example by an acetyl group (Ac) as follows.

[0252] In a 1L two-necked flask, 53.4 g PPFS-gS-PTMC-OH-01 (1 equivalent) are solubilized in 600 mL of DCM. Then, 18.6 mL of TEA (5 equivalents) are added to the solution. After 10 min of stirring, 9.4 mL of acetyl chloride are added dropwise. The reaction medium is kept stirring for 24 h at room temperature. After reaction, the reaction medium is precipitated in ethanol.

[0253] After drying, a viscous, transparent, yellowish polymer is obtained. It is named "PPFS-gS-PTMC-OAc-01" or "PPFS-g 0.5 -S-PTMC 3700 -OAc".

[0254] The protection of the -OH chain ends is confirmed by 1< H NMR analysis (CDCl 3 , 298K, 400MHz) ( figure 13 ).

[0255] The side chain hydroxyl functions of the PPFS-gS-PTMC-OH-02 copolymer synthesized in Example 3.2 can also be protected according to the same protocol. The resulting polymer is named "PPFS-gS-PTMC-OAc-02" or "PPFS-g 0.4 -S-PTMC 5500 -OAc". Example 4 Preparation of a poly(2,3,4,5,6-pentafluorostyrene) comb polymer carrying poly(ε-caprolactone) grafts (PPFS-gS-PCL) 4.1 Preparation of a telechelic poly(ε-caprolactone) (PCL) ("SH-PCL-OH-01")

[0256] 0.55 g of diphenyl phosphate (0.5 equivalents) are introduced into a two-necked flask containing a magnetic stirrer. The two-necked flask is fixed on a condenser. The assembly is placed under vacuum and then under argon flow. 15 mL (30 equivalents) of ε-Caprolactone (ε-CL) and 60 mL of anhydrous toluene are added. After a few minutes of stirring, 0.6 mL (1 equivalent) of mercapto hexan-1-ol is added to the reaction medium. The reaction medium is heated to 50°C for 90 min. After this time, 0.48 mL (1.02 equivalents) of triethylamine (TEA) is added to the reaction medium to stop the polymerization. The reaction medium is concentrated, then precipitated in methanol (MeOH). The product, in the form of a white semi-crystalline polymer, is recovered by filtration and dried under vacuum for 48 h. This product is named "SH-PCL-OH-01".

[0257] The polymer is characterized by nuclear magnetic resonance (NMR) of 1< H ( Figure 14). It is also characterized by CES (THF, 30°C, universal calibration).

[0258] It is deduced that the molar mass of the synthesized polymer is about 3000 g / mol. 4.2 Preparation of a PPFS comb polymer carrying poly(ε-caprolactone) grafts (PPFS-gS-PCL) PPFS-gS-PCL 3000 -OH ("PPFS-gS-PCL-OH-01")

[0259] 1.3 g of SH-PCL-OH-01 synthesized in Example 4.1 (1.5 equivalents) and 0.051 g of PPFS-03 synthesized in Example 1.1 (1 equivalent) are introduced into a 50 mL two-necked flask. 15 mL of MEK are used to solubilize the reagents. After solubilization, 0.025 mL of DBU is added to the reaction medium. The reaction medium is kept stirring for 20 h at room temperature.

[0260] After this reaction time, the reaction medium is directly precipitated in cold MeOH. The product, in the form of a white semi-crystalline polymer, is obtained after filtration and dried under vacuum for 48 hours. This product is named "PPFS-gS-PCL-OH-01". The polymer obtained is characterized by nuclear magnetic resonance (NMR) of 1< H (CDCl 3 , 298K, 400MHz) ( Figure 15 ) and 19< F (CDCl 3 , 298K, 400MHz) and by CES (THF, 30°C, TDS calibration)) ( figure 16 ).

[0261] The formation of the comb polymer is confirmed by CES analysis. Example 5 Preparation of electrolytes and electrochemical properties

[0262] The comb polymer "PPFS-gS-PTMC-OAc-01", synthesized in Examples 3.1 and 3.3 (762 mg), is mixed with lithium salt LiTFSI (112.5 mg) in THF at 56°C.

[0263] After evaporation of the solvent, the electrolyte is dried under vacuum at 80°C. The solid electrolyte is then incorporated into a symmetrical wedge (stainless steel) / electrolyte / wedge (stainless steel) button cell for the determination of its ionic conductivity by EIS (Electrochemical Impedance Spectroscopy).

[0264] Solid electrolytes are also prepared and incorporated into button cells according to a protocol similar to that described previously, based on the following comb polymers: comb polymer PPFS-g 0.4 -S-PTMC 5500 -OAc, named "PPFS-gS-PTMC-OAc-02", synthesized in examples 3.2 and 3.3; comb polymer PPFS-g 0.2 -S-PTMC 5000 -OAc, named "PPFS-gS-PTMC-OAc-03", synthesized according to a protocol similar to that described in examples 2 and 3 from PPFS-03 (example 1.1), whose grafting rate is 20%, the molar mass of the side chains is approximately 5000 g / mol and the ends of the side chains have been protected by an acyl group; comb copolymer PPFS-gS-PCL 3000 -OH, named "PPFS-gS-PCL-OH-01", and synthesized in Example 4, whose molar mass of the side chains is about 3000 g / mol and the ends of the side chains have not been protected.

[0265] In all these electrolytes, the amounts of comb polymers and lithium salt are adjusted so that the molar ratio CO 3 / Li (in the case of PTMC grafts) or CO 2 / Li (in the case of PCL grafts) is 15.

[0266] There figure 18 represents the evolution of the ionic conductivity of the polymer electrolytes formed as a function of temperature and demonstrates good ionic conductivity. List of cited documents

[0267] [1] Mindemark et al., Progress in Polymer Science, 81:114-43 (2018). [2] Bocharova et al., Macromolecules, 53:4141-57 (2020). [3] Bouchet et al., Innovations technologiques (2015). [4] Li et al., Progress in Polymer Science, 122:101453 (2021). [5] EP 3 865 533 A1. [6] EP 3 865 532 A1. [7] Atanasov et al., Solid State Ionics, 9 (2013). [8] Hiorns et al.. Polymer, 43:3365-9 (2002). [9] EP 3 763 748 A1.

[10] Fukushima, Chapter 7, Polymer Chemistry Series, Cambridge: Royal Society of Chemistry (2018).

[11] Makiguchi et al, Macromolecules, 44:1999-2005 (2011).

[12] Makiguchi et al., Macromolecules, 46:1772-82 (2013).

[13] Liu et al.. Polym Chem, 7:5526-35 (2016).

[14] Zhu et al., Polymer, 80:88-94 (2015).

[15] Zhu et al., European Polymer Journal, 80:234-9 (2016).

[16] Zhu et al., Sci Rep, 8:3734 (2018).

[17] Yin, Thiol-para-fluoro modified PPFS as building blocks for the design of silica-based nanocomposite and layer by layer self-assembled thin films (2018).

[18] Yin, European Polymer Journal, 10 (2018).

Claims

1. Process for preparing a comb polymer comprising at least the steps consisting in: (i) providing a polymer formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers, referred to as "PPFS-type polymer", which is intended to form the main chain of the comb polymer; (ii) providing at least one polymer, referred to as "telechelic polycarbonate / polyester", which is intended to form side chains of said comb polymer, said polymer being formed from at least one five- to eight-membered cyclic monomer chosen from lactones and cyclic carbonates, and having at least one hydroxyl function at one of its ends, and a free thiol function; and (iii) grafting said telechelic polycarbonate / polyester, in the para position of a portion of the pentafluorophenyl groups of the monomer units of the PPFS-type polymer, said grafting involving a nucleophilic substitution reaction between the thiol function borne by the telechelic polycarbonate / polyester and the fluorine atom at the para position of the pentafluorophenyl group.

2. Process according to the preceding claim, wherein said nucleophilic substitution reaction for grafting said telechelic polycarbonates / polyesters in step (iii) is performed in the presence of an aprotic base that is weaker than sodium hydride, sodium hydroxide and potassium hydroxide, preferably in the presence of an aprotic base having a pKa of strictly less than 15 and strictly greater than 10, in particular strictly less than 14, more particularly less than or equal to 13, or even between 10.2 and 13, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) or triethylamine (TEA).

3. Process according to Claim 1 or 2, wherein said PPFS-type polymer is a poly(2,3,4,5,6-pentafluorostyrene).

4. Process according to any one of the preceding claims, wherein said PPFS-type polymer has a number-average molar mass Mn, determined by size exclusion chromatography, of greater than or equal to 10 000 g.mol-1, in particular of between 10 000 g.mol-1 and 1 000 000 g.mol-1, in particular between 40 000 g.mol-1 and 600 000 g.mol-1, more particularly of between 40 000 g.mol-1 and 400 000 g.mol-1.

5. Process according to any one of the preceding claims, wherein said telechelic polycarbonate / polyester is formed from one or more monomers chosen from trimethylene carbonate and ε-caprolactone, and in particular is a poly(trimethylene carbonate) (PTMC) or poly(ε-caprolactone) (PCL) having a free thiol function at one of its ends and at least one hydroxyl function, preferably just one hydroxyl function, at the other of its ends.

6. Process according to any one of the preceding claims, wherein said telechelic polycarbonates / polyesters employed in step (ii) are obtained beforehand in a single step by ring-opening polymerization of said cyclic monomer(s), in the presence of at least one initiator that is a mono- or polyalcohol, in particular monoalcohol, bearing a free thiol function, in particular a mercapto alkanol, for example 6-mercaptohexan-1-ol; and of a catalyst, preferably an organic catalyst and more preferentially chosen from diphenyl phosphate (DPP) and 1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (BNPH).

7. Process according to any one of the preceding claims, wherein said telechelic polycarbonates / polyesters have a polydispersity index, defined as the ratio of the weight-average molar mass Mw to the number-average molar mass Mn, these being determined by size exclusion chromatography, of strictly less than 1.2, preferably of between 1 and 1.1.

8. Process according to any one of the preceding claims, wherein said telechelic polycarbonates / polyesters have a number-average molar mass, determined by 1H NMR analysis, of strictly greater than 2000 g.mol-1, especially of between 2000 g.mol-1 and 20 000 g.mol-1, in particular of between 2500 g.mol-1 and 10 000 g.mol-1, and more particularly between 3000 g.mol-1 and 7500 g.mol-1.

9. Process according to any one of the preceding claims, wherein said telechelic polycarbonate(s) / polyester(s) and said PPFS-type polymer are employed in step (iii) in a telechelic polymers / monomer units of the PPFS-type polymer molar ratio of between 0.1 and 1.

10. Process according to any one of the preceding claims, further comprising at least one step of purifying the comb polymer obtained at the end of the grafting (iii), said purification step being performed by dissolving the polymer obtained at the end of step (iii) in an organic solvent, for example in dichloromethane (DCM), acetone, tetrahydrofuran (THF), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), or mixtures thereof, preferably DCM, and then by precipitating the comb polymer in a mixture of a first solvent chosen from methanol, ethanol, diethyl ether, and mixtures thereof, and of a second solvent chosen from DCM, acetone, THF, MEK, DMF, and mixtures thereof, in particular in an acetone / methanol mixture, followed by liquid / solid separation, for example filtration, and drying.

11. Process according to any one of the preceding claims, further comprising a step of protecting the hydroxyl functions present at the ends of the polycarbonate / polyester side chains of said comb polymer, by reaction with at least one compound, referred to as protecting agent, chosen from acyl chlorides, acid anhydrides and isocyanates.

12. Comb polymer, comprising a main chain of PPFS type formed from 1-ethenyl- and / or 1-allyl-2,3,4,5,6-pentafluorobenzene monomers, a portion of the monomer units of the main chain bearing polymeric side chains, referred to as polycarbonate / polyester chains, formed from at least one five- to eight-membered cyclic monomer chosen from lactones and cyclic carbonates; said polymeric side chains being grafted in the para position of the pentafluorophenyl groups via thioether bonds.

13. Comb polymer according to the preceding claim, said polymer being obtained by the process defined according to any one of Claims 1 to 11.

14. Comb polymer according to Claim 12 or 13, having a degree of grafting of side chains, determined by 19F fluorine nuclear magnetic resonance (NMR), of greater than or equal to 1% and less than or equal to 100%, preferably of between 5% and 90%, in particular of strictly greater than 35%, especially of between 38% and 75%, and more particularly between 40% and 60%.

15. Solid electrolyte, in particular of solid polymer electrolyte (SPE) or hybrid solid electrolyte (HSE) type, comprising, or even being formed of: - at least one comb polymer as obtained according to the process of any one of Claims 1 to 11 or as defined according to any one of Claims 12 to 14, of which the hydroxyl functions at the ends of the grafted side chains are preferably protected; - at least one alkali or alkaline earth metal salt, in particular a lithium salt; and - optionally one or more inorganic fillers.

16. Electrochemical system, in particular an energy storage device, especially a rechargeable battery, in particular a lithium battery, comprising a solid electrolyte, in particular a film of solid electrolyte, as defined in Claim 15.

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